A low alloy sintered steel contains at least 0.15 percent by weight and less than 0.8 percent by weight of carbon. Its matrix is formed by a tempered martensite containing prior austenite crystal grains of not more than 15 μm in mean grain size. Pores and nonmetallic inclusions contained in the matrix are not more than 50 μm in maximum diameter, and the density of the low alloy sintered steel is at least 96 percent of theoretical density. A raw material powder for forming the low alloy sintered steel includes iron alloy powder which is prepared by an atomizing process, and is treated with a dry mill in an inert gas atmosphere or in the atmospheric air. Thus, dislocations are introduced into the raw material powder, and nonmetallic inclusions contained in the raw material powder are pulverized to be not more than 50 μm in maximum diameter. Not only static characteristics but also dynamic characteristics, such as fatigue strength, of the low alloy sintered steel are improved.

Low alloy sintered steel and method of preparing the same

Sintered ferrous alloys of at least 95 % theoretical density are obtained by sintering a powder mixture containing atomised copper-free ferrous alloy, copper phosphide and, optionally, copper, copper alloy and/or graphite to provide a sintered alloy containing, in percentages by weight, 0.6-2.5 % carbon, 2-8 % chromium, 4.2-20 % copper, 0.5-10 % molybdenum, 0.4-1.2 % phosphorus, 1-20 % tungsten, 1-5 % vanadium, and optionally, up to 12 % cobalt, up to 2 % manganese and up to 2 % nickel with the balance being iron and less than 2 % impurities. The % carbon content is in the range CCC % - 0.1 % to CCC % + 0.3 % (where CCC % is the calculated carbon content = (CWE/20) - 0.4 and CWE = % tungsten content + twice % molybdenum content + six times % vanadium content) and the copper phosphide contains 2 to 14 % phosphorus. The sintered compact is cooled at a rate which prevents hardening and can subsequently be machined and/or heat treated.

High density sintered ferrous alloys

A high temperature wear resistant sintered alloy suitable for the material of a valve seat in an automotive vehicle engine. The matrix of the sintered alloy consists essentially of carbon ranging from 0.45 to 1.15% by weight, nickel ranging from 5.4 to 27% by weight, molybdenum ranging form 0.4 to 2.7% by weight, cobalt ranging from 4.2 to 7.2% by weight and balance being substantially iron. The matrix is formed of a mixture of at least one of sorbite structure and bainite structure and austenite structure. Furthermore, the matrix includes hard phase dispersed therein and containing at least silicon, molybdenum and cobalt. The sintered alloy of such a structure can exhibit high strength and wear resistance at high temperatures regardless of type of engine and kind of fuel in case of being used as the material of the valve seat, while maintaining production cost thereof lower.

High temperature wear resistant sintered alloy

Embodiments of the present invention relate to methods of forming powder metals materials and parts. More specifically, certain embodiments of the present invention relate to methods of forming powder metals materials and parts by densifying at least a portion of a surface of the materials and/or parts after sintering and prior to densifying one or more core regions of the materials and/or parts. Other embodiment provide powder metal parts, such as gears and sprockets, having surface regions that are uniformly densified to full density to depth ranging from 0.001 inches to 0.040 inches, and core regions that can have at least 92 percent theoretical density and further can have essentially full density, or full density. Still other embodiments relate to brazed, welded, plated and gas-tight powder metal parts and components that can be made in accordance with the various non-limiting methods disclosed herein.

Powder metal materials and parts and methods of making the same

A powder metal steel alloy composition for high wear and temperature applications is made by water atomizing a molten steel alloy composition containing C in an amount of at least 3.0 wt%; at least one carbide-forming alloy element selected from the group consisting of: Cr, V, Mo or W; an O content less than about 0.5 wt%, and the balance comprising essentially Fe apart from incidental impurities. The high carbon content reduces the solubility of oxygen in the melt and thus lowers the oxygen content to a level below which would cause the carbide-forming element(s) to oxidixe during water atomization. The alloy elements are thus not tied up as oxides and are available to rapidly and readily form carbides in a subsequent sintering stage. The carbon, present in excess, is also available for diffusing into one or more other admixed powders that may be added to the prealloyed powder during sintering to control microstructure and properties of the final part.

Powdered metal alloy composition for wear and temperature resistance applications and method of producing same

A method for forming high carbon hard alloys using powdered metal techniques wherein the carbon content of the atomized powdered metal particles is minimized and the carbon content to achieve the desired composition is provided by blending carbon or carbon containing powder with the powdered metal particles prior to compaction and sintering. The compact may be sintered just above the solidus temperature of the alloy.

Gordon Russell Lohman

Papers

Method of producing high carbon hard alloys